DTC P1586 - Transmission Encoding Signal Not Rational

Install scan tool. Start engine and check if DTC P1586 is present. If DTC is present, go to next step. If DTC is not present, problem is intermittent. See INTERMITTENTS in TESTS W/O CODES article.
Turn ignition off. Check circuit between transmission range switch and ECM terminal No. 86. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit or terminal is okay, check transmission range switch. See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article. Replace as necessary. If switch is okay, clear DTC. See CLEARING CODES under Self Diagnostic System section. Retest system. If DTC resets, replace ECM.